Motor boat muffler



June 1965 D. R. PHILLIPS 3,191,714

MOTOR BOAT MUFFLER Filed July 9, 1963 0 5 j r 'pfrl I II 1 I I: 1 I l I L 23 114 2:2 25 0! INVENTOR.

li I DONALD R. PHILLIPS F G 3 ATTORNEYS United States; Patent "ice 3,191,714 MOTOR BOAT MUFFLER Donald R. Phillips, 2503 th St., Santa Monica, Calif.

Filed July 9, 1963, Ser. No. 293,746 5 Claims. (Cl. 181-44) This invention relates generally to engine mufilers and more particularly, to .an improved motor boat muffler adapt-ed to surround the exposed portion of the motor exhaust pipe extending from the transom of a motor boat.-

Marine mufiiers generally are well known in the art and take 'various different forms. Usually, these mufflers, as in the case of automobile mufilers, are adapted to beinserted between the exhaust pipe and the manifold outlet-s from the engine. Installations of this type, however, require structural modifications in the exhaust pipe itself as well as time and labor to insert the mufiler. Further, many boats do not have suflicient space or adequate access to enable an internal installation. Also, the muffler must be designed for a particular diameter exhaust pipe structure in order to operate most efficiently and enable installation thereof.

With the above in mind, it is a primary object of this invention to provide an improved type of marine of motor 7 beat mufller in which the mufller itself is adapted to be secured to the boat transom in a position surrounding the exposed portion of the exhaust pipe to the end that installation may readily be effected without modification of the exhaust system.

More particularly, it is an object to provide an improved motor boat muffler which is readily attachable to the exterior transom of the boat itself in a position to surround the exhaust and yet operate effectively to mufile sounds from the exhaust with a greater degree of efliciency as compared to conventional known motor boat mufilers.

Another object is to provide an improved mufiler which increases in efficiency with increasing engine velocity.

Another object is to provide an improved muffler designed to break up cooling water circulated through the exhaust to effect an absorption of noxious fumes present in the exhaust gases.

Still another important object of this invention is to provide an improved motor boat muffler which may be manufactured in a standard size and which includes means enabling severance of portions of the muffler to vary its eflective size and thus render it adaptable to exhaust pipes of different diameters.

Another object is to provide a muffler which exhibits negligible back pressure to the end that engine efficiency is not impaired by the use of the muffler.

Briefly, these and many other objects and advantages of this invention are attained by providing a muffler in the form of outer and inner coaxial casings adapted to be secured to the rear surface of the boat transom in .a position to surround the extending portion of the motor exhaust pipe. The walls of the respective casings define a tapered annular passage therebteween. The inner casing wall includes a plurality of holes so that communication is provided between the exhaust pipe Within the inner casing and this annular passage. The outer and inner casings themselves terminate in tapered outlet portions, the outlet openings thereof being approximately equal to the diameter of the exhaust pipe itself. These tapered portions in turn define a tapered annular passage connecting with the first mentioned annular passage to 3,191,714 Patented June 29, 1965 define a venturi sect-ion. The arrangement is such that the exhaust gases will be divided, some of the gases passing axially through the casing structures and the other gases passing through the holes in the inner casing to the annular passages. The gases passing out the annular passage and the straight through gases will be traveling at different velocities and will result in cancellation of sound waves in each of the gas streams when the gases leave the mufller structure.

In accordance with further features of the invention, there may be provided a diverter secured to the inner wall of the inner casing and tapered in a direction opposite to the tapered portions of the outer and inner casings. This diverter serves to deflect part of the gases from the exhaust pipe to the various holes in the inner casing and will enable a considerable reduction in length of the muffler without impairing its effectiveness,

In addition to the foregoing structure, the tapered portions of the outer and inner casings are provided with a step configuration enabling sections thereof to be readily severed or separated from the remaining port-ions so that the overall size of the muflie-r outlet openings may be varied to accommodate different diameter exhaust pipes.

A better understanding of the invention will be had by now referring to a preferred embodiment thereof as illustrated in the accompanying drawings, in which:

FIGURE 1 is a fragmentary perspective view of the rear portion of a motor boat illustrating the mufller of this invention secured to the boat transom;-

FIGURE 2 is an enlarged cross-section taken in the direction of the arrows 22 of FIGURE 1; and

FIGURE 3 is another cross-section taken in the direction of the arrows 33 of FIGURE 2.

Refer-ring first to FIGURE 1, there is illustrated a motor boat transom 10 to which the muffler 11 of this invention is secured in a position to surround the exhaust pipe.

With particular reference to FIGURES 2 and 3, the exhaust pipe is illustrated at 12. As shown, the muffler 11 includes an outer casing havinga cylindrical body portion 13 terminating at one end in a flange 14. Cooperating with this outer casing is an inner casing having a truncated conical body portion 15 provided with aplurality of holes 15. This truncated conical body portion terminates in a flange 15 cooperating with the flange 14 and fastenings 17 to secure the inner and outer casings to the transom -10.

As shown in FIGURE 2, the far end of the cylindrical 'body portion 13 of the outer casing terminates in an outer tapered outlet portion 18 defining an outlet opening '19 of substantially equal diameter to the diameter D of the exhaust pipe 12. Similarly, the far end of the inner casing '15 terminates in an inner tapered outlet portion .20 defining an outlet opening 21. The Walls of these outer and inner tapered portions define a tapered annular passage 22 merging with the tapered annular passage defined between the cylindrical body portion 13 and truncated conical body portion 15 of the inner and outer casings to define a venturi section.

The mufiler may also include an annular diverter structure 23 secured to the inside wall of the inner casing 15 at its junction point with the inner tapered portion 20 as shown. The taper of the diverter 23 is in a direction opposite to the taper of the tapered portions 18 and 20 and serves to deflect gases from the exhaust pipe 12 towards the holes 15' in the inner casing body 15.

In a preferred embodiment of the invention, the exterior wall of the outer tapered portion 18 is provided with an annular step configuration as indicated at 13' and the interior wall of the inner tapered portion 20 is similarly provided with a step configuration 20. Also the annular diverter is stepped as shown at 24. With this arrangement, definite index points are provided at which the tapered end portions may be severed to vary the diameter of the outlet openings 19 and 21 and the inlet opening of the diverter. Such separated portions are indicated at dotted lines in FIGURE 2 at 18", 2t)" and 23'. As an example, the steps may be graded in units of one-half inch so that the diameter of the outlet openings 19 and 21 may be varied in steps of one-half inch by suitably severing the tapered outlet portions at the appropriate step. For most etlicient operation, it is desirable that the diameter of the outlet opening 19 correspond substantially to the diameter D of the exhaust pipe 12. The opening 20 and opening of the diverter 23 are each approximately three-fifths the area of the opening 19. Thus, if a larger diameter exhaust pipe 12 is used, the same muffler may be attached and suitable sections of the tapered portions severed to provide the desired correspondence in diameters.

With all of the diameters dimensioned as described, there is provided a straight through passageway through which approximately one-half the gases from the exhaust will pass. However, as a consequence of divergence of the gases from the end of the exhaust pipe 12 and the presence of the diverter, approximately one-half of the gas will pass through the openings 15'.

In order to add strength to the casing structures, they may be provided with lateral ribs such as indicated at 25 and 26 for the outer and inner casing walls respectively. These lateral ribs extend in an axial direction and are preferably uniformly distributed about the exterior of the casing, the ribs 26 falling between the various openings 15' for the inner truncated conical body portion 15 of the inner casing.

With the foregoing description of the various components in mind, the operation of the mufiier will now be described. With the various sections properly dimensioned in accordance with the diameter D of the exhaust pipe 12, the muffler may readily be secured over the exhaust pipe in coaxial relation therewith and secured to the rear transom of the boat as by the bolts or screws 17. This operation is very simple and does not require access to any interior portion of the boat. Further, it does not require any dismantling or modification on the exhaust pipe structure itself or of the engine manifold.

With the mufiler installed as described, gases from the exhaust pipe 12 will divide, first gases passing axially through the outlet openings 19 and 21 and other diverging portions of the gases passing through the openings 15' to the'annular venturi passage 22. Because of the diverter structure and longer path for the diverging gases passing through the holes 15', the gas streams through the openings 19 and 21 and through the annular passage 22 will travel at different velocities. While the theory of operation is not exactly known, it is believed that as a consequence of these different velocities, sound cancellation takes place there being a substantially complete mulfiing of the sound from the motor. In this respect, the use of the annular passage defining a venturi section in cooperation with the straight through outlet passage openings 19 and 21 results in negligible back pressure, the straight through gases tending to pull the gases from the venturi section therethrough. Moreover, as a consequence of this design, it is found that when the engine speed is greatly increased, the resulting increase in velocity of the exhaust gases renders the muffler even more efficient in its sound eliminating properties.

From the foregoing description, it will thus be evident that the present invention has provided a greatly improved motor boat muffier. Not only is the overall mufiler itself relatively short in length, but it may be manufactured relatively inexpensively and substantially no labor costs are involved in the installation.

While only one particular embodiment has been set forth and described, various changes that fall clearly within the scope and spirit of this invention will occur v to those skilled in the art. The motor boat muffler is therefore not to be thought of as limited to the one example set forth merely for illustrative purpose What is claimed is:

1. A motor boat muffler adapted to be secured .to a boat transom to surround the exposed portion of the motor exhaust pipe extending from said transom, comprising, in combinationyan outer casing having a cylindrical body portion of larger diameter than said exhaust pipe terminating at one end in flange means for securement to said transom and at its other end in an outer tapered outlet portion; an inner casing having a truncated conical body portion substantially co-extensive with said cylindrical body portion and decreasing in diameter from said one end of said body portion towards said other end, said truncated conical body portion having one end secured to said one end of said cylindrical body portion and its other end terminating in an inner tapered outlet portion of similar taper angle .to said outer tapered outlet portion so that there is defined a venturi section between the walls of said outer and inner casings; and an annular diverter structure secured at one end to the inside wall of said inner casing at the junction point of its truncated conical body portion and its inner tapered outlet portion, said diverter structure tapering towards a reduced diameter opening in a direction opposite to said outer and inner tapered portions, said truncated conical body portion having a plurality of openings therein whereby a portion of the gases exhausted from said exhaust pipe is deflected by said diverter structure to pass through said openings into said venturi section.

2. A mutller according .to claim 1, in which said outer and inner tapered portions respectively include annular step configurations in their outer and inner wall surfaces respectively so that the sections thereof are marked for severance from the remaining portions to enable the outlet diameters of said outer and inner tapered portions to be varied in accordance with the diameter of said exhaust pipe.

3. A mufiler according to claim 2, in which the outer surface of said cylindrical body and said truncated conical body portions include a plurality of lateral ribs extending in the direction of the axis of said exhaust pipe and uniformly circumferentially distributed about said por tions.

4. A mufiler according to claim 3, in which the outlet opening of said outer tapered portion is at least equal to the diameter of said exhaust pipe outlet, and the outlet of said inner tapered portion and the opening of said diverter structure are each equal to approximately threefifths the area of said outlet opening of said outer tapered portion.

5. A mufiler comprising, in combination: an outer casing having a cylindrical body portion for receiving gases in one end, the other end terminating in an outer tapered portion; an inner casing having a truncated conical body portion substantially co-extensive with said cylindrical body portion and decreasing in diameter from said one end of said body portion towards said other end, said truncated conical body portion having one end secured to said one end of said cylindrical body portion and its other end terminating in an inner tapered outlet portion of similar taper angle to said outer tapered outlet portion so that there is defined a venturi section between the walls of said outer and inner casings; and an annular diverter structure secured at one end to the inside wall of said inner casing at the junction point of its truncated conical body portion and its inner tapered outlet portion, said diverter structure tapering towards a reduced diameter opening in a direction opposite to said outer 5 6 and inner tapered portions, said truncated conical body 1,561,859 11/25 Kemble 181-60 portion having a. plurality of openings therein whereby a 2,829,730 4/ 58 Barkelew 181-46 X portion of the gases received is deflected by said diverter 3,036,653 5/62 Calabresi 181-44 structure to pass through said openings into said venturi 3,121,469 2/64 Schelf 18152 X 5 FOREIGN PATENTS References Cited by the Examiner 579,275 24 France.

UNITED STATES PATENTS 409,631 2/45 877,431 1/08 Jones 181*61 X LEO SMILOW, Primary Examiner. 

5. A MUFFLER COMPRISING, IN COMBINATION: AN OUTER CASING HAVING A CYLINDRICAL BODY PORTION FOR RECEIVING GASES IN ONE END, THE OTHER END TERMINATING IN AN OUTER TAPERED PORTION; AN INNER CASING HAVING A TRUNCATED CONICAL BODY PORTION SUBSTANTIALLY CO-EXTENSIVE WITH SAID CYLINDRICAL BODY PORTION AND DECREASING IN DIAMETER FROM SAID ONE END OF SAID BODY PORTION TOWARDS SAID OTHER END, SAID TRUNCATED CONICAL BODY PORTION HAVING ONE END SECURED TO SAID ONE END OF SAID CYLINDRICAL BODY PORTION AND ITS OTHER END TERMINATING IN AN INNER TAPERED OUTLET PORTION OF SIMILAR TAPER ANGLE TO SAID OUTER TAPERED OUTLET PORTION SO THAT THERE IS DEFINED A VENTURI SECTION BETWEEN THE WALLS OF SAID OUTER AND INNER CASINGS; AND AN ANNULAR DIVERTER STRUCTURE SECURED AT ONE END OF THE INSIDE WALL OF SAID INNER CASING AT THE JUNCTION POINT OF ITS TRUNCATED CONICAL BODY PORTION PORTION AND ITS INNER TAPERED OUTLET PORTION, SAID DIVERTER STRUCTURE TAPERING TOWARDS A REDUCED DIAMETER OPENING IN A DIRECTION OPPOSITE TO SAID OUTER AND INNER TAPERED PORTIONS, SAID TRUNCATED CONICAL BODY PORTION HAVING A PLURALITY OF OPENINGS THEREIN WHEREBY A PORTION OF THE GASES RECEIVED IS DEFLECTED BY SAID DIVERTER STRUCTURE TO PASS THROUGH SAID OPENINGS INTO SAID VENTURI SECTION. 